A dynamical approach to ancilla assisted quantum thermometry

TL;DR

This paper introduces a dynamic quantum thermometry scheme where a sensor interacts with an ancilla to improve temperature sensitivity without requiring initial entanglement or joint measurements, by converting incoherent bath information into measurable coherences.

Contribution

The proposed method uniquely uses a Hamiltonian-driven interaction to enhance thermometry sensitivity without entanglement or joint measurements, differing from prior approaches.

Findings

Transforms bath information into meter coherences

Does not require initial entanglement

Avoids joint measurements

Abstract

A scheme for improving the sensitivity of quantum thermometry is proposed where the sensing quantum system used to recover the temperature of an external bath is dynamically coupled with an external ancilla (a meter) via a Hamiltonian term $\hat{H}_I$. At variance with previous approaches, our scheme relies neither on the presence of initial entanglement between the sensor and the meter, nor on the possibility of performing joint measurements on the two systems. The advantages we report arise from the fact that the presence of $\hat{H}_I$ interferes with the bath-sensor interaction, transforming the sensor into an effective transducer which extracts the intrinsically incoherent information on the bath temperature, and maps it into coherences in the meter where it can finally be recovered by local measurements.